1. Field of the Invention
The invention relates to synergistic antimicrobial combinations of iodopropargyl compounds with 1,2-benzisothiazolin-3-one and use of such combinations in controlling fungal and/or bacterial growth in aqueous systems, particularly in metalworking fluids, such as soluble-oil, semi-synthetic and synthetic metalworking fluids.
2. Description of Related Art
Iodopropargyl compounds, i.e. compounds containing a propargyl group and an iodine on the acetylenic carbon, are known to be useful in controlling bacteria and fungi in various aqueous systems. U.S. Pat. Nos. 4,259,350; 4,719,227; 4,616,004; 3,923,870; and 4,592,773, incorporated herein by reference, set forth various examples of iodopropargyl compounds with microbicidal properties.
One such iodopropargyl compound is iodopropargyl carbamate. The preparation and use of iodopropargyl carbamate as a microbicide and a preservative is described in U.S. Pat. No. 4,945,109; the disclosure of which is incorporated herein by reference.
Another such iodopropargyl compound is 3-iodopropargyl-N-butylcarbamate (IPBC). This compound is manufactured and sold by Troy Chemical Company under various names such as Polyphase.RTM. product, Polyphase.RTM. AF-1 product, and Polyphase.RTM. NP-1 product.
Although good microbicides, iodopropargyl compounds are expensive. Systems requiring high concentrations of iodopropargyl compounds are generally uneconomical.
The compound 1,2-benzisothiazolin-3-one has been used to control microbial growth for a long time. This compound is sold as Proxel.RTM. CRL product, or Proxel.RTM. GXL product.
As can be seen in Examples 1, 2 and 3, Table 1 (see Samples 8-10), and Tables 2 and 3 (Samples 15-18), high concentrations of 1,2-benzisothiazolin-3-one are required to control both bacterial and fungal growth in metalworking fluids.
Both of these types of products are used alone to control microorganisms in industrial fluids, since many industries, such as the machining industry, experience problems caused by microorganisms. Aqueous metalworking fluids or cutting fluids used in the machining industry are particularly susceptible to fouling caused by microorganisms. In machining operations, metalworking fluids are used primarily to reduce friction and heat, thereby reducing wear and prolonging the life of equipment.
Unfortunately, metalworking fluids have properties which are ideal for the growth of bacteria and fungi. Although bacteria are important in the biodeterioration of metalworking fluids, fungi and yeast play an important role as well. (Bennett, E.O., "The Deterioration of Metalworking Fluids", Prog. Industrial Microbiology, 13:121 (1974)).
Frequently, these microorganisms can cause the buildup of microbial deposits on machine surfaces, the clogging of jets and lines, the deterioration of the properties of the metalworking fluid itself, enhanced corrosion, and health and odor problems. When affected or deteriorated by the growth of microorganisms, the metalworking fluid loses many of its essential properties. The pH of the fluid may drop and other chemical changes may occur until the fluid can no longer provide adequate lubrication. At this point, the fluid must be replaced with fresh fluid, which is costly and results in loss of production time.
As a result of these problems, biocides are used extensively in metalworking fluid systems. Biocides may be incorporated in fluid concentrate or added to diluted fluids once they are in the holding tanks of the machine works.
There are many commercially available biocides. Some are of questionable utility because they have undesirable odors, or create hazards with respect to storage, use or handling. Consequently, workers in the trade have continued to seek improved biocides.
Economic factors, particularly the cost of the biocide and the expense of its application, can also be important factors when choosing a particular biocide for use in metalworking fluid systems. The cost performance index of any biocide is derived from the basic cost of the material, its effectiveness per unit weight, the duration of its biocidal or biostatic effect in the system treated, and the ease and frequency of its addition to the system treated.
Workers in the trade continue to seek a commercially available biocide capable of exhibiting a prolonged biocidal effect at normal use levels. Physical conditions, such as temperature and chemical reactivity with ingredients present in the system, often diminish or eliminate the effectiveness of prior art biocides known to the inventors. For example, many systems contain organic material which may react with a specific biocide and render the biocide ineffective.
Metalworking fluid systems in which heavy microbial growth occurs can especially benefit from the practice of the present invention. The practice of the present invention can also benefit many other aqueous systems, whether or not heavy microbial growth occurs, because of the reduction in frequency and quantity of the use of biocides.